A rolling motion reducing apparatus is known, which reduces a rolling motion of a moving apparatus such as a ship. For example, Japanese patent publication JP Heisei 7-215280 A (corresponding to U.S. Pat. No. 5,628,267 A) discloses a ship oscillation suppression device and a ship. This ship oscillation suppression device has a control moment gyro (100). In the oscillation suppression device, a spin shaft (60) of a flywheel (1) of the gyro (100) is driven by a flat type spin motor (5) and is supported by a gimbal (2) through spin bearings (6). The gimbal (2) is supported by supports (8) through gympal shafts (3) and gimbal bearings (7). The oscillation of the gimbal shaft (3) is braked by disk brakes (30). The disk brake (30) includes a gimbal shaft connection fixing disk (9) and a support connection fixing disk (10). Or, the oscillation of the gimbal shaft (3) is braked by powder brakes (40) or oil dampers (11).
The above ship oscillation suppression device is an apparatus that, by supporting the flywheel which is rotating at high speed with the gimbal, when the gimbal is swung due to the rolling motion of the ship, the gyro torque (the counter torque) caused by the gyro effect is transmitted to the ship body, thereby reducing the rolling motion of the ship. In the above mentioned ship oscillation suppression device, the gyro torque is braked by braking the oscillation of the gimbal shafts with the braking devices such as the disk brakes, the powder brakes and the oil dampers.
With respect to the above rolling motion reducing apparatus, the inventors have now discovered the following facts. That is, in the above rotational motion reducing apparatus, the braking devices that brake the swinging motion of the gimbal shafts are provided. However, mechanisms that make the rolling motion reducing apparatus stop urgently in an emergency are not provided. In other words, in the case that the gimbal of the rolling motion reducing apparatus operates excessively, the braking devices are only mechanisms for suppressing the excessive gimbal operation. Therefore, for example, in the case that the braking device is in malfunction in which the braking device cannot fulfill its function due to the temperature increase, there is the potential that the gimbal is swung violently and the rolling motion reducing apparatus breaks down.
Furthermore, in the above rolling motion reducing apparatus, when the braking device is in malfunction, in order to make the rolling motion reducing apparatus stop urgently, it is necessary to turn off a power switch of the motor of the flywheel and wait for completely stopping of the flywheel. However, it takes long time to completely stop the flywheel. If the rolling motion reducing apparatus is left for a long time when the braking device is in malfunction, since the gimbal operates continuously for along time while the braking device still remain in malfunction, there is the potential for causing the braking device to break down.
Moreover, as a method of temporarily stopping the rolling motion reducing apparatus in order to confirm an effect of the rolling motion reducing apparatus installed in the ship on the sea, turning off the power switch of the motor is the only method. Then, after turning off the power switch, it is necessary to wait for completely stopping of the rolling motion reducing apparatus for a long time. However, since a situation of waves that the ship body receives may be varied, it is difficult to confirm the effect of the rolling motion reducing apparatus under an equivalent wave condition as an input to the ship body. In addition, it is difficult to experience the effect of the rolling motion reducing after a long time passing.
As the related technique, Japanese patent publication JP 2010-256042 A (corresponding to US patent publication US 2011030604 A1) discloses a rolling motion reducing apparatus for a ship. This rolling motion reducing apparatus for a ship includes a flywheel; a gimbal; a motor; a gimbal supporting section; a first damper; a motor driver; and a safety unit. The gimbal supports the flywheel rotatably. The motor drives the flywheel. The gimbal supporting section supports the gimbal such that the gimbal can rotate. The first damper brakes a rotational motion of the gimbal. The motor driver supplies driving power to the motor. The safety device makes the motor driver stop to the supply of driving power when a temperature of the first damper exceeds a predetermined temperature.